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t=1787566351; bh=WhPzGv/jLYWIV5rqDmfbQ8SCSY37BPj6+XKV+nPgTVw=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=WozWsLt+jB/GwRyOYpg2/YGtYULCzHHuEJpJhazxcp8ETvCFkDdwRoNSym+MQGejs sw07//fH8xUWLNlxFkxJBqDzZsOv+VCC2oqyFOow2V8rtcYQJKa2W4zk5uWoXRe2wp vf4lN/qY4ylXf6s3RQURtB7g2gceM8spgXjsx7diC+PjElapTxuzpe8ejROVGvwVCq jVuk7WRd/TamkCkgLV08AarxtRCXlQ7pPvAKelcSJWZyn1W5+T3XUBGRlPRxXAj7vc RWD+iWeIXKXjzq+5rHjyQnKXZCkHlwJvaYoyfO1OE3Fv210uvY1zUsJYQrH1aX/jSN rKQjxGzwSEZvg== Message-ID: <19de764c-467d-4472-8c85-a84de87bb702@kernel.org> Date: Mon, 24 Aug 2026 12:12:26 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/mempolicy: Fix sleeping allocation in alloc_pages_bulk_weighted_interleave() To: Eric Dumazet , Andrew Morton Cc: linux-kernel , syzbot+0dbf6d295b3350944f0b@syzkaller.appspotmail.com, Zi Yan , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , linux-mm@kvack.org References: <20260821170407.3721004-1-edumazet@google.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 9CE71A0005 X-Stat-Signature: ddhrm6mtqfydbaq3gf6mjh4tnpkjfght X-HE-Tag: 1787566352-97700 X-HE-Meta: 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 ZTEgmLdn 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/21/26 19:04, Eric Dumazet wrote: > syzbot reported a sleeping function called from invalid context splat > in bucket_table_alloc(). > > When rhashtable_insert_slow() rehashes the table under rcu_read_lock(), > it calls bucket_table_alloc(..., GFP_ATOMIC | __GFP_NOWARN). > If the bucket table allocation uses vmalloc, __vmalloc_node_range_noprof() > invokes vm_area_alloc_pages() -> alloc_pages_bulk_mempolicy_noprof() with > the passed GFP_ATOMIC flags. > > If the current task has an MPOL_WEIGHTED_INTERLEAVE mempolicy, > alloc_pages_bulk_weighted_interleave() is called and currently hardcodes > GFP_KERNEL when allocating the temporary weights array, triggering > a might_alloc() splat in atomic/RCU contexts. > > Pass the gfp flags (masked with GFP_RECLAIM_MASK to strip page-allocator > zone modifiers like __GFP_HIGHMEM) received by > alloc_pages_bulk_weighted_interleave() to kmalloc() instead of > hardcoding GFP_KERNEL. Since the weights buffer is immediately > initialized in full, kmalloc() is sufficient. > > Fixes: fa3bea4e1f82 ("mm/mempolicy: introduce MPOL_WEIGHTED_INTERLEAVE for weighted interleaving") > Reported-by: syzbot+0dbf6d295b3350944f0b@syzkaller.appspotmail.com > Closes: https://lore.kernel.org/lkml/6a88837e.ae6ddae5.3da009.0040.GAE@google.com/T/#u > Signed-off-by: Eric Dumazet > --- Acked-by: David Hildenbrand (Arm) -- Cheers, David